414 SOILS: PROPERTIES AND MANAGEMENT 



mine the so-called " feeding power " of the plant, are 

 recognized by the popular terms " weak feeder " and 

 " strong feeder," applied, on the one hand, to such 

 crops as wheat or onions, which require very careful soil 

 preparation and manuring, and, on the other hand, to 

 maize, oats, or cabbage, which demand relatively less 

 care. In the manuring and rotating of crops, this differ- 

 ence in absorptive power must be considered, in order not 

 only to secure the maximum effect on the crop manured, 

 but also to get the greatest residual effect of the manure 

 on succeeding crops. 



331. The absorptive power of cereals. Cereals have 

 the power of utilizing the potassium and phosphorus of 

 the soil to a considerable degree, but they generally re- 

 quire fertilization with nitrogen salts. Most of the cereals, 

 such as wheat, rye, oats, and barley, take up the principal 

 part of their nitrogen early in the season, before the nitri- 

 fication processes have been sufficiently operative to fur- 

 nish a large supply of nitrogen; hence nitrogen is the 

 fertilizer constituent that usually gives the best results, 

 and should be added in a soluble form. Wheat, in partic- 

 ular, needs a large amount of soluble nitrogen early in 

 its spring growth. Since it is a " delicate feeder," it does 

 best after a cultivated crop or a fallow, by which the 

 nitrogen has been converted into a soluble form. Oats 

 can make better use of the soil fertility and do not require 

 so much manuring. Maize is a very coarse " feeder," 

 and, while it removes a large quantity of plant-food from 

 the soil, it does not require that this shall be added in a 

 soluble form. Farm manure and other slowly acting 

 manures may well be applied for the maize crop. The 

 long growing period required by the maize plant gives it 

 opportunity to utilize the nitrogen as it becomes avail- 



